In operation, many components of internal combustion engines are exposed to extremes of temperature and pressure as well as to corrosive environments. Furthermore, such components often operate at very high repetition rates. Fluid control devices of internal combustion engines, such as fuel injector valves, intake valves and exhaust valves, are also required to maintain their dimensional tolerances under such extreme conditions. The prior art has long sought methods, materials and techniques for enhancing the durability and service life of internal combustion engines and their respective components. Toward this end, various components of the engines have been coated with protective materials.
Any such coating should function to protect engine components from extreme operating conditions. In addition, the coatings should decrease friction and/or be wear resistant. In addition, any such coatings should be easy and economical to apply in a high volume production process. The prior art has heretofore encountered problems in implementing such coatings since many of the desired criteria are mutually exclusive. For example, ceramic coatings are very hard and chemically inert; however, such coatings tend to be abrasive, and they are often brittle. Diamond-like carbon coatings have also been investigated for use in internal combustion engines. Such coatings also tend to be brittle; furthermore, scale up of processes for preparing such coatings has been found to be difficult.
Disclosed in the prior art are a number of coatings which have been proposed for use in fluid control systems of internal combustion engines. For example, U.S. Pat. No. 5,783,261 discloses a fuel injector valve which is coated with amorphous carbon that is implanted with a carbide forming material such as silicon, titanium or tungsten. PCT publication WO 01/61182 discloses a fuel injector needle having a coating of diamond-like carbon which contains large amounts of metal carbides. U.S. Pat. No. 5,237,967 discloses a valve lifter coated with an amorphous carbon film including 30-50 atomic percent of hydrogen therein. Similar teachings are found in U.S. Pat. Nos. 5,771,873 and 5,249,554. Ceramic coatings for fuel injector components are disclosed in U.S. Pat. Nos. 5,309,874 and 6,267,307.
Despite the various attempts implemented in the prior art, there has heretofore been no satisfactory coating for use in fluid control devices of internal combustion engines. As will be explained hereinbelow, the present invention provides a hard, lubricious, chemically inert coating for internal combustion engine components. The coating of the present invention is wear resistant, yet it is durable under conditions of repeated mechanical shock. The coatings of the present invention can be deposited by high volume, easy to control sputtering techniques, and have been demonstrated to significantly increase the service life of engine components. These and other advantages of the invention will be apparent from the drawings, discussion and description which follow.